The aggregation of magnetic cations in a semiconductor

Recent theoretical and experimental studies indicate that semiconductor/ferromagnetic metal nanocomposite systems may exhibit novel and hitherto unexplored functionalities in spintronics, but also in photonics and thermoelectrics. We summarise our studies [1-5] demonstrating that it is possible to fabricate (Ga,Fe)N where the Fe ions are distributed in the nitride matrix in a controllable way giving rise either to a diluted random alloy or to chemical decomposition into (Ga,Fe)N regions more or less rich in the magnetic component or to ferromagnetic FeNx nanocrystals buried in the GaN host. The aggregation of the Fe cations exhibits a strong dependence on the growth-rate and -temperature, allowing – when appropriately mastered – a control of the solubility limit. Moreover, the formation of the Fe-rich nanocrystals and, hence, the ferromagnetic response of (Ga,Fe)N can be affected by doping with donors and acceptors. Our findings confirm the hypothesis that the attractive force between magnetic cations can be adjusted by varying their charge state [6].